The invention relates to a dowel bolt comprised of a bolt having a leading end in the setting direction and an opposite, trailing end with an outer thread at the trailing end, and an expansion head and an expansion sleeve in the leading end region that is expanded by the expansion head.
Dowel bolts of the type described above are used in fastening objects to a structural component. A bore hole is created in the structural component, whose diameter corresponds approximately to that of the outer diameter of the bolt or is even somewhat less with respect to the bolt. The dowel bolt is set in the bore hole by one or several strokes with a hammer, for example. Due to the relative movement of the bolt, particularly that of the conical part of the expansion head to the expansion sleeve, it friction-lockingly rests on the inner wall of the bore hole and expands radially so as to anchor the dowel bolt in the structural component, and in particular in the bore hole.
DE 296 02 513-U1 discloses a dowel bolt comprised of a bolt having at one end an outer thread and on the opposite end a cone and an expansion sleeve, which expands in the setting direction.
In particular, when using a worn drill bit for creating a bore hole, the dowel bolt can be inserted into the bore hole only by applying considerable force, for example, by hammer impact. This has the drawback that the bore hole and/or the dowel bolt can be damaged and consequently the required loads can no longer be accommodated or the required setting depth and thus the load level is not assured.
The object of this invention is to provide a dowel bolt that can be economically manufactured and, by virtue of its visual appearance in the set condition, provides feedback relative to the quality of its anchorage.
The object is achieved according to the invention in that the bolt has, on its trailing end facing away from the setting direction, at least one peripheral recess with a indentation.
By virtue of the fact that at least one recess is arranged on the trailing end face of the bolt facing away from the setting direction, a plastic change occurs on the trailing end face when inserting the bolt. Depending on the magnitude and number of impact blows acting upon the trailing end face in particular hammer blows, the indentation itself changes as does the area of the end face abutting the indentation. The deformations in the set condition allow, on the basis of their appearance, conclusions to be made regarding the quality of the anchorage and in this fashion act as setting controls. Because of the arrangement of the recess in the peripheral zone of the trailing end face of the bolt opposite the setting direction, the deformations occur when inserting the dowel bolt into the bore hole. Moreover, it is also possible, for example, by virtue of the peripheral arrangement of the recess to make conclusions regarding the direction of the impacts. Ideally, impact is applied in the axial direction of the bolt; this creates a uniform deformation in the recess. If the impact acts at an angle to the axis of the bolt it will also be evident in the deformation of the recess. A further advantage offered by the recess is in the accommodation of material, compacted by the impact, of the trailing end face of the bolt. This prevents an excessive deformation of the external circumference of the bolt in the area of the trailing end face and assures that a load bearing means, a nut for example, can easily be attached to the trailing end face of the bolt.
The recess is advantageously configured open towards the external periphery of the bolt to assure deformation of the trailing end face of the bolt. In other words, the recess is open on the trailing end face and on the circumferential periphery of the bolt adjacent the trailing end face. Further, the recess being open to the outer periphery of the bolt prevents an excessive expansion of the outer periphery of the bolt due to the compacted material occurring when inserting the bolt. In addition, a further embodiment of the recess in the zone of the outer periphery has a web with a minimal wall thickness in order to provide a closed outer periphery.
The radially outer part of the recess advantageously exhibits an approximately triangular cross-section to allow inexpensive manufacture of the dowel bolt.
Advantageously, the recess forms on the trailing end face of the bolt opposite to the setting direction and radially inwardly of the triangular cross-section, a rectangular opening which allows inexpensive manufacture of the dowel bolt. In a further embodiment, the recess on the trailing end face of the bolt facing away from the setting direction exhibits a trapezoidal-shaped opening.
In order to assure optimal deformation of the trailing end face by the action of the impacts at the time of insertion of the bolt, for example, preferably two corresponding recesses are arranged diametrically opposite to each other.
The recess advantageously has at least one spacing or separation a from the central axis of the bolt, the separation corresponding to 0.15 to 0.35 times the diameter of the bolt, to assure optimal load bearing by the bolt.
The depth of the recess preferably corresponds to 0.03 to 0.08 times the diameter of the bolt so as to enable economical manufacture of the bolt. In addition, this assures that on the one hand there is no occurrence of impairment of the loading of the dowel bolt and on the other hand the recesses are easily recognized for example by the user or by a setting control machine.
In order to optimally dimension the deformation of the recess at the time of setting the bolt, the maximum width of the depth of the recess extending in the circumferential direction of the bolt corresponds to 0.05 to 0.2 times the diameter of the bolt.
Advantageously, four recesses are uniformly spaced around the periphery of the bolt so as to assure easily recognizable deformation irrespective of the direction of the impact acting on the face end of the bolt opposite to the setting direction in the setting process.